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New Technology

Understanding how bats use the landscape or interact with wind turbines can help us inform decisions for properly siting wind energy facilities or minimize the direct impact of wind turbines on bats.

GPS Technology

Hoary bat with GPS tag Photo Courtesy of Cris Hein

The miniaturization of GPS tags (light enough to secure to bats) is allowing researchers to investigate the long-term and long-distance movements of migratory bats.

“This technology helps us understand better how they’re using the landscape,” says Michael Schirmacher, BCI Wind Energy Program Manager. “By learning migratory pathways with GPS technology, for example, we may be able to identify migratory pathways or activity hotspots, and better inform siting new turbines to avoid having to implement relatively costly minimization strategies.”

Thermal Imaging Cameras

Bat and turbine Photo Courtesy of Michael Schirmacher

High-resolution thermal cameras are also allowing BCI and its research partners to better see what even tiny 12-gram bats are doing at night around the turbines. The U.S. Geological Survey has been a key partner in this work, and in developing software and methodologies to help streamline analysis of the resulting footage.

By comparing video data with environmental information already being collected by the turbines themselves—wind speed, humidity and temperature—researchers can pinpoint which bats are dying, when and where, and under what conditions, to even further define dangerous conditions for bats. If we can understand and predict risk to bats, then our strategies to reduce or avoid impact may be more cost effective, increasing the potential for large scale adoption.

“For a long time, we’ve had to look on the ground for dead bats under turbines, and could only identify that a bat died the night before and what the average conditions were,” explains Cris Hein, BCI Director of Wind Energy. “Getting real-time conditions on when bats are near turbines is helpful for refining operational minimization or possibly identifying the best places to position ultrasonic acoustic deterrents. These cameras have really opened the door to a better understanding of bat behavior and timing around wind turbines.”

Ultrasonic Acoustic Deterrents (UADs)

There’s some evidence to suggest that bats, at least some species, are attracted to wind turbines, but what that is, if anything beyond sheer curiosity, remains unknown.

One promising solution Bat Conservation International’s wind program team, under the auspices of the BWEC, is investigating the effectiveness of Ultrasonic Acoustic Deterrents, or UAD devices, mounted on the wind turbines themselves.

The idea is that these devices will “jam” bats’ echolocation or make the airspace around the turbine aurally uncomfortable, thereby keeping bats away from potential dangerous rotating turbine blades. Researchers got the idea from some species of moth's ability to "jam" bat calls in order to avoid predation.

Ultrasonic Acoustic Deterrents (UADs) are devices that emit a loud, high frequency noise (sound human can’t hear) - and that bats will avoid. It is hypothesized that placing UADs on wind turbines may allow wind energy facilities to operate normally while dramatically decreasing bat fatalities.

The tricky thing is to produce a robust device that can withstand being exposed to the environmental conditions experienced 80 to 100 m above ground level, and be effective at deterring bats away from large rotor-swept areas of current and future turbines. Field trials have shown promise but testing on operating turbines provide technological and logistical challenges that are currently being refined. If proven, UADs could provide an alternative impact reduction strategy that is more cost effective than operational minimization allowing wind turbine operators more options to reduce impacts to bats.

Field tests are still under way to determine how well the devices perform under various environmental conditions, how effective they are compared to operational minimization and which species can be deterred by the devices mounted on to of operating wind turbines.

BCI is planning three studies in 2017 to investigate the effectiveness of a UAD-designed and manufactured by Renewable NRG Systems (RNRG). One of these, funded by the U.S. Department of Energy, will compare the reduction levels of the deterrents with operational minimization, specifically feathering blades to 5.0 m/s (or 2.0 m/s above the preset operating conditions). Moreover, we will combine both impact reduction strategies to determine whether there is an additive effect, furthering the reduction in bat fatalities.

Preliminary functionality tests of the RNRG deterrent, conducted in 2016, showed significant improvements over previous generations of the technology. The devices passed all reliability tests, both in the lab and when installed on wind turbines, and showed no water entry or overheating (both issues commonly experienced in the previous design). During ground-based tests of the device, we documented a significant reduction in bat activity in areas of high bat concentrations (e.g., ponds where bats drink and forage for insects).

BWEC

Mission:The Bats and Wind Energy Cooperative (BWEC) is an alliance of experts from government agencies, private industry, academic institutions, and non-governmental organizations that cooperate to develop and disseminate solutions to reduce to the greatest extent practicable or, where possible, prevent mortality of bats at wind energy facilities.

Wind energy research with USGS and BCIPhoto Courtesy of Michael Schirmacher

In 2003, Bat Conservation International became a founding member of the BWEC, along with the American Wind Energy Association, the U.S. Fish and Wildlife Service and the National Renewable Energy Laboratory. Each of these organizations are represented on the BWEC Oversight Committee. Later, the U.S. Geological Survey, U.S. Department of Energy and the Association of Fish and Wildlife Agencies joined the BWEC Oversight Committee. Members of government agencies, private industry, academia and NGOs are represented on the Science Advisory and Technical Advisor Committees. Together these three committees establish research priorities and peer-review reports prior to dissemination.

The BWEC is organized and managed by a Project Coordinator (a full-time employee of Bat Conservation International) and 3 committees, each of which is comprised of leading experts in their field and held on a voluntary basis.

Oversight Committee – responsible for direction of the BWEC.

Science Advisory Committee – responsible for scientific guidance to the Program Coordinator and Oversight Committee.

The BWEC is the foremost organization for research related to bats and wind energy development. The Cooperative spearheaded initial evaluation of operational minimization in the U.S. and has 10 years of experience studying use of ultrasonic acoustic deterrents to reduce bat fatalities at wind turbines.

In addition to being the leader in testing impact reduction strategies for bats, the BWEC is focused on several additional priorities, including:

Dennis Krusic (USFS)

Scott Darling (Vermont FWD)

TBD

Operational Minimization

Currently, the most effective method of reducing bat fatalities at wind turbines is to employ a strategy known as operational minimization, alternatively known as curtailment. This strategy limits blade rotation, the primary cause of bat fatalities, during high risk periods (e.g. low wind, fall migration period). Bat Conservation International, under the auspices of the Bats and Wind Energy Cooperative (BWEC) was the first to test this strategy in the U.S., demonstrating that bat fatalities could be reduced up to 93 percent. Estimated loss of wind generation was 1–3% of the annual power production. The actual power loss can vary by site and effect power purchase agreements, that is why BCI and others are investigating ways to optimize this strategy to make it more economically viable, and developing alternative strategies, such as Ultrasonic Acoustic Deterrents

Operational Minimization: A twofold strategy of feathering turbine blades (i.e., positioning the blades parallel to the wind) and raising the wind speed at which the blades begin spinning and generating electricity (aka the cut-in speed) to slow rotation at lower wind speeds.

Raising the cut-in speed (the wind speed at which the spinning turbine blades begin to generate electricity) by 4.9 to 9.8 feet per second (1.5 to 3.0 meters per second) above the manufacturer’s preset speed is an effective impact reduction strategy because most bat fatalities occur at relatively low wind speeds. Thus, keeping the blades from spinning until wind speed reach 16 to 20 feet per second (5.0 to 6.0 meters per second) can significantly reduce bat fatalities for relatively little loss in power generation - since at many sites the majority electricity is generated at higher wind speeds.

There is even an opportunity to reduce bat fatalities with little to no loss in power. By simply feathering the turbine blades (pitching them parallel to the wind so they are moving slowly) below that preset speed, bat fatalities can be reduced by an average of 35 percent. In fact, this is a supported best management practice by the American Wind Energy Association (AWEA) and a mitigation measure in the World Bank’s Environmental, Health, and Safety Guidelines for Wind Energy

A great deal of the work BCI has been pursuing in the wind arena in recent years requires a better understanding of how, why, where, when, and which species of bats are killed at wind facilities, with the aim of a more precise operational minimization strategy that has minimal impact on electricity generation.

Wind facility at sunset Photo Courtesy of Michael Schirmacher

Cris Hein, Director of BCI’s wind energy program, said he thinks it’s very possible to devise even more specific operational minimization recommendations. But it requires much more information—including details like the exact time of night bats tend to interact with wind turbines, weather data, such as temperature and barometric pressure, and exact wind speeds and direction.

"In my mind, you couldn’t ask for an easier fix,” Hein said. “In most situations, it’s only required at night, under certain wind conditions, and for a couple months out of the year. Even at a core scale, that’s pretty well refined. But we’re trying to see if we can narrow it down even more, by looking at other variables the industry could use to reduce the conditions under which curtailment should be used.”

“We do have a collaborative relationship with the industry, and this is an opportunity to work with them to find a solution,” Hein said.

However, currently only a few wind energy facilities implement operational minimization unless they developed Habitat Conservation Plans with the U.S. Fish and Wildlife Service. Though an effort by the wind industry and the U.S. Fish and Wildlife Service to develop a multi-state Habitat Conservation Plan covering eight states in the Midwest is currently under review.

“We have the goal of working collaboratively to resolve this issue that meets everybody’s needs,” Hein said. “Not only BCI’s goals of protecting bats, but also in being able to generate renewable electricity. But until we can find a solution that’s accepted by the conservation community and federal agencies, and is cost-effective enough for the industry to buy into, we have our work ahead of us.”

Bats & Wind Energy

Dead hoary bat next to a turbine Photo Courtesy of Michael Schirmacher

The conservation calculus for wind energy changed dramatically in the fall of 2003. Up until that point, bird fatalities had been the primary environmental concern at wind turbines, particularly raptors. Then a study in West Virginia estimated 1,400 to 4,000 bat fatalities during late-summer and autumn, and the concerns about environmental impacts of wind power began to change across North America.

What causes bat fatalities?

Current research suggests that the overwhelming majority of bat fatalities are caused by collisions with turbine blades. There is some evidence to suggest that a phenomenon known as barotrauma may result in a small proportion of bat deaths, as well. Barotrauma involves tissue damage to air-containing structures, such as lungs, caused by rapid or excessive pressure change. Air pressure changes can occur at the edges of moving turbine blades and may help explain some bat fatalities.

Fatalities

Between 2000 and 2011, an estimated 650,000 to 1.3 million bats have died from collisions with wind turbines in the United States and Canada (Arnett and Baerwald 2013). Additionally, as many as 400,000 estimated fatalities may have occurred in 2012.

With wind-generated energy expected to expand from the current 82,000 MW to 224,000 MW by 2030 (U.S.DOE Wind Vision 2015), the impact on bat populations from this build-out could be devastating unless solutions to minimize fatalities are developed and implemented.

In the U.S. and Canada, at least 24 species of bats have been reported as killed by wind turbines. The hoary bat (Lasiurus cinereus), eastern red bat (Lasiurus borealis) and silver-haired bat (Lasionycteris noctivagans), all migratory tree bats, account for nearly 78% of the kills north of Mexico. The hoary bat accounts for 38% of the fatalities. A new study that looked at hoary bat mortality at wind energy facilities during 2014 revealed that populations of the species may plunge by a staggering 90 percent in the next 50 years if no action is taken.

At some sites in the Midwest and Eastern U.S., species that are already battered by White-nose Syndrome (WNS), can account for up to 60% of wind-energy fatalities.

Two federally endangered species, the Hawaiian hoary bat (Lasiurus cinereus semotus) and the Indiana myotis (Myotis sodalis), also have been killed by turbines.